1. Field of the Invention
This invention concerns a throttle control for use with equipment having an engine which is adapted for use in either a positive-action or negative-action mode. The throttle control hereof includes a shifter coupled to a control cable and moveable in a circular path, the shifter being reversibly held between the surrounding case for orientation in either a positive-action or negative-action position.
2. Description of the Prior Art
Many types of power implements such as lawn mowers, tillers, and the like are powered by internal combustion engines which are operable at different speeds. Typically a Bowden cable having an outer sheath and an inner control wire are connected between the throttle of the engine and a throttle control mounted on the handle or other handy location. In use, the throttle may be actuated by shifting a lever to move the wire toward and away from the throttle.
In some instances, the orientation of the engine throttle makes it advantageous to have the engine at an open throttle or maximum speed with the control wire extended toward the control (negative-action), and decrease engine speed by pushing the wire away from the control and relatively toward the throttle. In this latter, closed-throttle position, the control lever is, by common practice, in a retracted position, i.e. pulled toward the operator. In other applications, it may be advantageous to have the engine at an open throttle or high speed with the control wire retracted toward the throttle and away from the control (positive-action), where the engine speed is decreased by pulling the control lever toward the operator to draw in the control wire toward the control. Typically, these types of action are independent and require separate designs of controls which must be independently manufactured.
It is also well known in the art to provide throttle controls which pivot. This pivot action is typically accomplished by a central pivot pin about which the shift lever moves in an arcuate path, as illustrated in U.S. Pat. Nos. 4,438,658 to Carlson and 5,000,059 to Barnard. However, in some circumstances a central pivot pin used to both hold the shifter in place and provide a pivot point may make pivoting undesirably difficult.
There has thus developed a need for a simple, economical throttle control which is inexpensive to manufacture, reliable in use, easy to shift, and which may be readily converted for use in either a positive-action or negative-action mode using the same components. Additionally, the shifter should be capable of detent-type action whereby at various points along the range of shifting movement, the throttle control presents preselected stops for holding the shifter against undesired movement which might be caused by vibration of the implement. Further, such a throttle control preferably may be converted between positive-action and negative-action modes before installation on the implement without the need for tools, but which can be partially assembled to prevent unintended disassociation of the components.
3. Summary of the Invention
These needs have been largely met by the throttle control in accordance with the present invention. The throttle control hereof is economical to manufacture and may be molded entirely of synthetic resin such as ABS. It is convertible for use in either a positive-action or negative-action mode. It presents a substantially circular bearing surface for engagement between the shifter and the supporting case which is spaced away from the pivot axis to provide ease in shifting. It also includes a minimum of components which can be releasably connected and separated without the need for tools prior to mounting on the implement.
In greater detail, the present invention includes a shifter and a case presenting first and second mating portions. The shifter is preferably integrally formed and includes a shift lever, a circular rim for defining a circular shift path, a positive-action control wire receiver and a negative-action control wire receiver. The shifter is positioned between first and second portions of the case and held therebetween, the case including a bearing wall which engages with the circular rim of the shifter to present a circular shift path. The bearing wall is spaced outwardly from the pivot axis and the case preferably includes an inner wall adapted to engage a follower provided on the shifter. Preferably the inner wall is provided with one or more recesses therein adapted to receive the follower at preselected points along the circular shift path.
The case and the shifter are configured to enable the shifter to be positioned in either a positive-action or a negative-action mode. The case includes a keeper for holding a mounting flange on the sheath surrounding the control wire, and a gap is provided in the bearing wall of one of the portions of the case to enable the control wire to pass therethrough. The lever of the shifter, which may be oriented at an angle or tangentially to the outer surface of the rim, may be provided with indicia on one side thereof useful in assisting the operator such as an indication of increasing throttle speed. Because the shifter can be reversed for either a positive-action or negative-action mode, the indicia can be presented for viewing by an operator in either mode by reversing the position of the shifter relative to the case. In either mode, the control wire remains in alignment with the gap in the rim, and only the particular positive-action receiver or negative-action receiver is changed.
The throttle control is readily mountable to a handle of the power implement by a single bolt passing through the pivot axis, but the bolt does not affect the force needed to move the shifter through its path of operation. The structure defining the aperture through which the mounting bolt passes also preferably defines a coupling member which includes a male clip associated with one of the portions of the case and a female tubular member presenting an internal catch on the other portion, whereby the coupling member can hold both sections and the shifter therebetween prior to final assembly on the handle of the power implement. The sections can be manually pulled apart without damage and without the need for tools, and then quickly clipped back together after, e.g., attaching the control wire to the desired positive-action or negative-action receiver.